The domain controllers respond to pings. The client accepts the first response and ignores subsequent responses. The response includes information about the domain controller’s site, the client’s site, and the closest bit value (which will be 1 if the domain controller is in the client’s site, and 0 if the domain controller isn’t in the client’s site).

If the returned closest bit value is 0, the client sends another DsGetDcName query to DNS.

This time, the client had more information about its site, so DNS can respond with an SRV RR list of domain controllers in the client’s domain and site.

The client sends out another round of LDAP-over-UDP pings to the domain controllers in the new list.

The first domain controller to respond with a closest bit value of 1 is the closest domain controller; the client will use this domain controller for further authentication.